Magnetorheological valve and devices incorporating magnetorheological elements

ABSTRACT

A valve used to control the flow of a magnetorheological fluid, in which the mechanical properties of the magnetorheological fluid are varied by applying a magnetic field, is described. The valve can comprise a magnetoconducting body with a magnetic core that houses an induction coil winding, and an hydraulic channel located between the outside of the core and the inside of the body connected to a fluid inlet port and an outlet port, in which magnetorheological fluid flows from the inlet port through the hydraulic line to the outlet port. Devices employing magnetorheological valves are also described.

This application is a division of application Ser. No. 07/973,113, whichwas filed on Nov. 6, 1992 now U.S. Pat. No. 5,353,839 issued Oct. 11,1994.

FIELD OF THE INVENTION

This invention relates to valves used in hydraulic devices employing amagnetorheological fluid, and more particularly to valves employed insystems in which a magnetic field is applied to the magnetorheologicalfluid, causing the properties of the magnetorheological fluid to vary.

BACKGROUND OF THE INVENTION

Valves designed for use with magnetorheological fluids are known in theart. As a fluid flows through such valves a magnetic field is applied tothe magnetorheological fluid. The interaction between the ferromagneticparticles in the magnetorheological fluid increases the effectiveviscosity of the magnetorheological fluid in the valve. This change inviscosity causes the resistance to the fluid flowing through the valveto increase, and causes a proportional change in the inlet pressure tothe valve, thereby slowing or stopping the fluid flow.

Known magnetorheological valves are generally large and consume a largeamount of power due to the large volume occupied by the hydraulic line.Known magnetorheological valves also have a high initial hydraulicresistance, which limits those valves to a narrow control range. Theresponse speed of these devices is generally slow.

Germer, U.S. Pat. No. 2,670,749, describes a valve for controlling theflow of fluids by means of a magnetic oil. Germer discloses a method ofcontrolling the flow of a fluid by passing the fluid through a magneticoil subjected to a magnetic field. When the magnetic oil becomesmagnetized, it thickens to a semi-solid state and offers increasedresistance to a flow of fluids passing through it.

A means for controlling the flow of a traditional fluid is also shown inJapanese Patent No. 63-83476. In the 63-83476 patent, a magnetic fluidpositioned within a magnetic inductor is used to drive an intermediateelement to control the flow of fluid through the valve.

Neither Germer nor Japanese Patent No. 63-83476 teaches a means forcontrolling the flow of the magnetic fluid itself. In addition, invalves such as those described in Germer and 63-83476, improvements inresponse time, power consumption, and overall dimensions are limited bythe capacity of the magnetic field to magnetize the magnetic fluid.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the invention to provide a magnetorheological valvesuitable for use with a magnetorheological fluid.

It is also an object of the invention to directly join the electronicand hydraulic parts of an hydraulic system without intermediatemechanical elements.

It is a further object of the invention to provide a magnetorheologicalvalve whose components enable the geometry of the hydraulic line to beoptimized, and the hydraulic resistance of the magnetorheological fluidflow to be thus controlled, so as to increase the speed of response andto widen the control range of hydraulic resistance of themagnetorheological valve and to reduce its overall dimensions and powerconsumption.

These and other objectives are achieved by a magnetorheological valvecomprising a magnetoconducting body with a magnetic core that houses aninduction coil winding, and an hydraulic channel located between theoutside of the core and the inside of the body connected to a fluidinlet port and an outlet port, in which magnetorheological fluid flowsfrom the inlet port through the hydraulic line to the outlet port. Theinvention further comprises a magnetorheological valve as described inwhich a portion of the core projecting beyond the coil winding isprovided with a movable element, one end of which is fitted with a conesection provided with a nonmagnetic spiral gasket located in a taperedbore, with the clearance between the cone section and the fixed coreforming the hydraulic line. The invention further comprises devicesincorporating such magnetorheological valves.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side cross-sectional view of a first embodiment of themagnetorheological valve of the invention;

FIG. 2 is a front cross-sectional view of a first embodiment of themagnetorheological valve of the invention;

FIG. 3 is a side cross-sectional view of a two-channel embodiment of themagnetorheological valve of the invention;

FIG. 4 is a side cross-sectional view of another embodiment of themagnetorheological valve of the invention;

FIG. 5 is a side cross-sectional view of a translational module of acommercial robot employing a valve of the invention;

FIG. 6 is a side view of a positioning pneumatic hydraulic driveemploying a valve of the invention;

FIG. 7 is a top plane view of the positioning pneumatic hydraulic driveof FIG. 6;

FIG. 8 is a side view of an exercise machine employing a valve of theinvention;

FIG. 9 is a side view of a vibration damping system used as a suspensionsystem for a driver's seat employing a valve of the invention;

FIG. 10 is a pneumatic magnetorheological drive employing a valve of theinvention;

FIG. 11 is a control system for hydraulic cylinder piston motionemploying a valve of the invention;

FIG. 12 is a system for stabilizing an object employing a valve of theinvention; and

FIG. 13 is a graph illustrating the effects of the magnetorheologicalvibration damping system of FIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In magnetorheological valves set forth in this application, amagnetorheological working fluid is pumped through a magnetorheologicalthrottle valve controlling element which, in a general case, is ahydraulic channel located in a magnetic field inductor. In response to acontrol signal, an electric current in the magnetizing coils of theinductor produces a magnetic field that varies the magnetorheologicalfluid viscosity in such a channel and results in a pressure drop in thevalve. The throttling valve is connected to, or integral to, a drive,and the pressure drop causes the force on the actuating element of thedrive to vary accordingly. The viscosity of the magnetorheologicalfluid, and corresponding pressure in the valve, may be held constant atany intermediate value, or may be varied until the valve ultimatelycloses. The magnetorheological valve thus provides quick-responsehydraulic resistance, which can be up to about 1 kHz in someapplications.

In FIGS. 1 and 2, there is shown a magnetorheological valve comprising amagnetoconducting body 1 housing an induction coil winding 2 with a core3. A core portion 4 of the core 3 projects beyond the coil winding 2,with an hydraulic line 5 formed by the surface of the projecting portionof the core 4 and the inside of the body 1. Coil winding 2 is connectedto a power supply source 11, such as a DC power supply, which isconnected to winding 2 through lines 12. Winding 2 preferably isshielded from direct contact with core 3 by at least partially enclosingwinding 2 in a nonmagnetic dielectrical coil body 13. The coil body 13is preferably made of plastic. One end of the hydraulic line 5 isconnected through an inlet port 6 with inlet pipe 14 which extendsthrough a nonmagnetic cover 10, as shown in FIG. 1. The other end ofhydraulic line 5 is connected to an outlet port 7, as seen in FIG. 2.Nonmagnetic seals 9 prevent leakage of the fluid from the hydraulicchannel 5. Seals 9 preferably comprise O-rings or other conventionalseals made from an elastomeric material. Notches 15 may be provided forconvenience in assembling the valve.

The design of the hydraulic line 5 increases the area of interaction ofa magnetorheological fluid with the magnetic flux, decreases themagnetic resistance, and raises the magnetic induction, with theampere-turns of the induction coil winding unchanged. It also increasesthe pressure differential in the hydraulic line, determined by thePousel expression ΔP=8μQL/πR⁴, where μ=viscosity, Q=flow rate, L=lengthof hydraulic line, and R=hydraulic radius. Where the other conditionsare held constant, ΔP will be larger for a longer hydraulic line L. In amagnetorheological valve according to the present invention, thehydraulic line L is made longer than in conventional magnetorheologicalvalves by directing a thin layer of magnetorheologicai fluid around thecircumference of the valve. Such an embodiment of the hydraulic lineincreases the increment of the pressure differential, with the overalldimensions of the magnetorheological valve substantially reduced.Magnetorheological fluids suitable for use with the value of theinvention are disclosed in two co-pending applications, U.S. Ser. No.868,466, entitled "Magnetorheological Fluids and Methods of MakingThereof" whose disclosure is incorporated herein by reference.

A partition 8 is located in the hydraulic line 5 between the inlet port6 and outlet port 7. Partition 8 preferably is made of a nonmagneticmaterial, with stainless steel particularly preferred.

Partition 8 enables the magnetorheological fluid to flow over the fulllength of the hydraulic line 5, increasing the length of hydraulic lineL in the Pousel expression and thereby increasing the pressuredifferential per unit power consumption. This will aid in reducing powerconsumption. If no partition is used, the fluid will flow in twodirections around the circumference from the inlet port 6 to the outletport 7. This two directional flow would reduce the length of hydraulicline L, since at least one stream of fluid would traverse one half orless of the hydraulic line and, as a consequence, the pressuredifferential would be reduced. The length of hydraulic line 5 betweenthe inlet 6 and outlet 7 ports in which partition 8 is locatedpreferably is less than the remaining length of hydraulic line 5. In aparticularly preferred embodiment of the invention, this distance isfrom about 5 to about 15 per cent of the length of the hydraulic line.If the distance between the inlet and outlet ports is less than about 5per cent of the length of the hydraulic line, partition 8 may becomeundesirably difficult to install in the manufacturing process. If thedistance between the inlet and outlet ports is greater than about 15 percent of the length of the hydraulic line, the working surface of thehydraulic line is not used efficiently. A distance between the inletport 6 and outlet port 7 of less than 15 per cent of the length of thehydraulic line permits maximum interaction between the fluid and themagnetic field, and maximizes the efficiency of the valve.

In operation, the magnetorheological fluid enters through inlet pipe 14into the inlet port 6, then fills the hydraulic line 5. Partition 8insures that the magnetorheological fluid flows in only one directionthrough hydraulic line 5 to outlet port 7. Application of power to coilwinding 2 induces a magnetic flux through body 1 and core 3. A magneticfield is established in the hydraulic line 5, with the magnetic lines offorce at right angles to the direction of the magnetorheological fluidflow. The magnetic field in the hydraulic line 5 affects themagnetorheological fluid viscosity, and as a consequence the pressuredifferential between the inlet and the outlet of the magnetorheologicalvalve is changed.

FIG. 3 shows a valve of the invention having a two-channel design.Similar to FIGS. 1 and 2, the magnetorheological valve in FIG. 3comprises a magnetoconducting body 301 housing an induction coil winding302 with a core 303. A portion of the core 304 projects beyond the coilwinding 302, and magnetic rings 318 are located between the body 301 andthe core 304 adjacent to the induction coil winding 302. First andsecond hydraulic channels 305A and 305B are formed by the surfaces ofthe projecting portion of the core 304 and the inside of the magneticrings 318. The hydraulic channel 305A is connected to an inlet pipe 314and to hydraulic channel 305B through a first internal channel 306A, asecond internal channel 317, and a third internal channel 306B. Eachhydraulic channel 305A, 305B is provided with a partition, similar tothat shown in FIG. 1 but not shown in FIG. 3, to direct the flow of themagnetorheological fluid over the entire length of the hydraulic line305A, 305B. Internal channel 317 is connected to an hydraulicaccumulator through connection pipe 316, which permits greater controlof the flow of magnetorheological fluid.

Hydraulic channel 305B is connected to internal channel 317 through aninternal channel 306B at one end, and to an outlet port 307 at the otherend. Nonmagnetic seals 309 prevent leakage of the fluid from thehydraulic channels 305. Nonmagnetic covers 319A and 319B assist inproviding the correct distribution of the magnetic flux in the valvemagnetic system. Nonmagnetic seals 321 prevent leakage ofmagnetorheological fluid from internal channel 317. Notches 320 may beprovided to facilitate assembly and repair of the valve.

In this embodiment, the magnetorheological fluid enters first hydraulicline 305A through inlet pipe 314, flows through first internal channel306A to internal channel 317, and flows through channel 317 to thirdinternal channel 306B. The fluid that enters third internal channel 306Bflows through second hydraulic line 305B to outlet port 307. Applicationof power to coil 302 induces a magnetic flux through body 301 and core303. A magnetic field is established in hydraulic lines 305A and 305B,with the magnetic lines of force at right angles to the direction of themagnetorheological fluid flow. The magnetic field in hydraulic lines305A and 305B affects the magnetorheological fluid viscosity, and as aconsequence the pressure differential between the inlet and the outletof the magnetorheological valve is changed. The two-channel embodimentof FIG. 3 can result in increased efficiency and pressuredifferentiation, even as compared to the valve embodiment of FIGS. 1 and2.

FIG. 4 illustrates an alternative valve of the invention. Themagnetorheological valve in FIG. 4 comprises a magnetoconducting body401 housing an induction coil winding 402 with a magnetoconducting core403. A portion of the core 404 projects beyond the coil winding 402. Asillustrated in FIG. 4, a portion 404 of the core projecting beyond coilwinding 402 may be provided with a magnetoconducting movable element425. An hydraulic channel 405 is formed by the surface of the projectingportion of the core 404 and the movable element of the core 425. One endof the hydraulic line 405 is connected via an internal channel 431,inlet channels 423, and an inlet port 406 to an inlet pipe 414, and theother end is connected via an outlet channel 430 to an outlet port 407.

Movable element 425 is connected to body 401 by a spring 426. One end ofmovable element 425 has a cone section 432, and the opposite end ofmovable element 425 is provided with a stop 424 located on the outsideof body 401. The cone section 432 of the movable element 425 is located,with a clearance 428, in a tapered bore 429 formed in the projectingportion 404 of the core 403. Hydraulic line 405 is located in theclearance 428 between the conical surfaces of the projecting portion ofthe core 404 and the cone section 432 of the movable element 425.

Such an embodiment enables a positive hydraulic resistance feedback andensures a low initial hydraulic resistance; the valve, when closed, willthen take less time to build up the pressure to a preset level. Inaddition, the possibility-of varying the flow area of the hydraulic lineand the flow change-over from axisymmetric to circumferential enable thecontrol range of hydraulic resistance to be widened.

One of the conical surfaces of the core 432 preferably is provided witha band-type nonmagnetic element 427 preferably arranged on theArchimedean spiral, which allows a minimum channel-forming clearance inin the magnetic circuit and changes the flow pattern from axisymmetricto circumferential. Such an embodiment also enables the control range ofhydraulic resistance to be widened.

The outside of the body 401 is completed, on the side of the movableelement 425, with a nonmagnetic cover 410 so that an inlet port 406 isformed. The inlet port 406 is connected to the hydraulic line 405 byinlet channels 423 and internal channel 431. Nonmagnetic element 418provides the correct distribution of the magnetic flux in themagnetorheological valve.

The magnetorheological valve illustrated in FIG. 4 operates as follows.A magnetorheological fluid is delivered to the inlet pipe 414, fillsinlet port 406, enters the hydraulic line 405 via the inlet channels 423and internal channel 431, then flows to the outlet port 407 throughoutlet channel 430.

When the magnetic induction coil 402 is energized, the resultingmagnetic field has an effect on the magnetorheological fluid flowing inthe hydraulic line. The magnetic interaction brought about in theclearance 428 between the movable element 425 and the projecting portion404 of the core 403 moves the movable element 425 in the axial directionso as to decrease the clearance 428. The magnetic force and thehydrodynamic force of the flow will exceed the elastic force of thespring 426 until the movable element 425 occupies, in the clearance 428,the position predetermined by the thickness of the band-type nonmagneticelement 427.

In this position the band-type nonmagnetic element 427 can function as aseal for the axisymmetric flow, and the magnetorheological fluid flowpath becomes circumferential on a spiral, with the stop 424 preventingthe movable element 425 from rotating around the longitudinal axis.

The hydraulic resistance of the valve is thereafter controlled byvarying the magnetizing current in the induction coil, i.e. the magneticfield strength in the clearance 428.

When the induction coil is de-energized, the movable element 425 isrestored to its original position by the spring 426.

The magnetorheological fluid and the magnetorheological valve may beemployed in a variety of applications, such as robot drives, dashpots,metering pumps, vibrators, and trainers. The magnetorheological fluidmay perform an "active" role in the function of the application, such ascausing an actuator to move a load, or may be a "passive" controllingelement slowing the movement of an actuator driven by another energycarrier. Among the useful applications are pneumatic positioning drivesand pneumohydraulic positioning drives, such as might be used in arobot, an exercise machine, a vibration damping system, and astabilization system. The magnetorheological valve enables one toimprove the operating characteristics and reliability of systems inwhich it is employed. The devices described herein as employingmagnetorheological valves can include any of the valves of theinvention.

A pneumatic positioning drive using magnetorheological elements is shownin FIG. 5. The drive provides system rigidity and broad dynamic velocitycontrol range. Such a drive also permits accurate positioning with nounwanted stops at any trajectory point and makes control throughoutdeceleration possible. Use of such a drive enables one to extend thefunctional potential of the simplest means of robotics (pneumaticrobots) due to a transition from a cycle to a circuit control. A drivesuch as the drive illustrated in FIG. 5 is relatively simple tomanufacture, reliable in operation, explosive-safe and is directlyconnected with the electronic units of the control system.

As can be seen in FIG. 5, a rodless end 544 of a cylinder 501 isconnected with a pneumatic system 535 via a connected-series hydraulicchannel 505, a first chamber 538, a second chamber 537 and a pneumaticdistributor 536. A second end 533 of cylinder 501 is connected directlywith pneumatic system 535. First and second chambers 538, 537 arepartitioned by a movable partition 540. Nonmagnetic seals 545 preventleakage of the fluid into pneumatic chamber 537, and nonmagnetic seals570 prevent leakage of the air from pneumatic chamber 537 into hydraulicchamber 538. A rod 541 is rigidly connected with an actuator 539. Thearea between the rodless end 544 of cylinder 501 and a head of piston534, the hydraulic channel 505, and the first chamber 538 are eachfilled with a magnetorheological fluid 543. Hydraulic channel 505containing fluid 543 acts as a clearance between the side surface ofpiston 534 and the inner surface of cylinder 501. Nonmagnetic seals 509prevent leakage of the magnetorheological fluid into second end ofcylinder 533. A magnetic field inductor coil 502 is mounted on the innersurface of a front cover 542 coaxially to rod 541. Cylinder 501, frontcover 542, rod 541 and piston 534 are made of magnetosoft material, andback cover 510 is made of nonmagnetic material.

The apparatus operates as follows. Depending on the required direction,pneumatic distributor 536 connects second chamber 537 either withpneumatic system 535, or with the atmosphere. A pressure drop on piston534 puts rod 541 and actuator 539 into motion. In this case,magnetorheological fluid 543 is displaced from first chamber 538 andflows through hydraulic channel 505 into the rodless end of cylinder544. A magnetic field induced by magnetic field inductor coil 502, viarod 541, piston 534, hydraulic channel 505, cylinder 501 and front cover542, affects fluid 543 being in hydraulic channel 505. In this case, thepressure drop in hydraulic channel 505 exerts a decelerating influenceon piston 534. Varying the current in magnetic field inductor coil 502regulates a speed of the actuator up to its complete stop and fixing ata required position.

A two-coordinate positioning pneumatic hydraulic drive usingmagnetorheological elements is shown in FIGS. 6 and 7. Such a drive isintended for programmed two-coordinate displacement in the space of acarriage.

A two-coordinate pneumatic drive is composed of two similar-operationdrives 646 and 647 as shown in FIG. 7. Each drive contains two maincylinders 601, each of which is partitioned by a piston 640 into apneumatic cavity 637 and an hydraulic cavity 638. Each pneumatic cavity637 is connected to a pneumatic distributor 636 via a pneumaticconnecting pipe 658. The location of pneumatic connecting pipes 658 isnot important to this invention; they may be arranged for convenience ofassembly. They are arranged for ease of illustration in FIG. 6. Eachhydraulic cavity 638 is filled with a magnetorheological fluid andconnected to a controlling magnetorheological hydraulic system, each ofwhich is composed of two magnetorheological valves 648, an hydraulicaccumulator 649, and connecting pipelines 659.

To illustrate, drive 646 contains two cylinders 601C and 601D. Cylinder601C is partitioned by a piston 640C into a pneumatic cavity 637C and anhydraulic cavity 638C. Cylinder 601D is partitioned by piston 640D intopneumatic cavity 637D and hydraulic cavity 638D. Pneumatic cavities 637Cand 637D are connected to pneumatic distributor 636 via pneumaticconnecting pipes 658C and 658D respectively. Hydraulic cavities 638C and638D are connected via hydraulic connecting pipes 659B, twomagnetorheological valves 648B and hydraulic accumulator 649B.

In each cylinder a flexible rope 650, which passes through hydrauliccavity 638, connects piston 640 to a pulley casing 653 by means of apulley unit 652. A carriage 651 moves over the external surface ofcylinders 601 by pulley casings 653 which form with the cylinders 601the rolling guides. A photoelectric position and velocity transducer654A is placed on the axis of pulley unit 652A, and transducer 654B isplaced on the axis of pulley unit 652D. Transducers 654A and 654B,magnetorheological valves 648A and 648B, and pneumatic distributor 636are connected by lines 661 to a program control device 655. In alternateembodiments, transducers 654A and 654B, magnetorheotogical valves 648Aand 648B, and pneumatic distributor 636 may be connected by other means,such as remote control. Carriage 651 is equipped with an actuator 639.Actuator 639 preferably is an hydraulic cutter, which is connected withan high-pressure source via a flexible pipeline 656. Drive 647 serves asa carriage for drive 646. The two-coordinate pneumatic drive issupported by a drive base 657.

A position circuit pneumatic hydraulic drive used for actuatordisplacement along one of the coordinates operates as follows. Thepneumatic distributor 636, which is controlled by program device 655,connects one of the pneumatic cavities 637C with the pneumatic system660 and the second cavity 637D with the atmosphere. In this case, piston640C of first cylinder 601C displaces the magnetorheological fluid fromits hydraulic cavity 638C into the hydraulic cavity 638D of the secondcylinder 601D through hydraulic connecting pipes 659B,magnetorheological valves 648B and hydraulic accumulator 649B. Piston640D of the second cylinder 601D, rope 650D, and carriage 651 move inguides 653C and 653D accordingly. An excess pressure is produced byhydraulic accumulator 649B in the magnetorheological hydraulic system,symmetric about its magnetorheological valves 648B, and as a result ofthis excess pressure and the connection of the ropes 650C and 650D withpistons 640C and 640D, movable elements--pistons 640, flexible rope 650,carriage 651--move substantially as a unit, thus providing a requiredrigidity of the drive. The excess pressure in the hydraulic system isalso necessary to lessen the effect of possible gas and air occlusionson the dynamics of the drive. A kinematic scheme of the mechanical andhydraulic parts of the drive is made so that under any operatingconditions the situation is possible where the magnetorheological fluidwould appear under rarefaction, i.e., the potential cavitation and lossof stable functioning of the drive is decreased.

When ropes 650C and 650D are moved, transducer 654B, which is mountedaxially on pulley unit 652D, generates electrical signals correspondingto the speed of carriage 651 and the position relative to the chosencounting base. Transducer signals enter device 655, are compared withthe program course and, as a result, device 655 outputs controllingsignals which are supplied to the magnetorheological valves 648B and thepneumatic distributor 636. The controlling signals induce a magneticfield in the valve windings, thus varying their hydraulic resistance upto complete shut-off; as a result, the drive motion and its position arecontrolled. Simultaneous shut-off of the two valves 648B stops the flowof magnetorheological fluid from hydraulic accumulator 649B to hydrauliccavity 638D and connecting lines 659B of the magnetorheologicalcontrolling hydraulic system, thereby providing the drive with rigidityat abrupt sign-variable loads at carriage 65i under the positioningconditions.

Drive 647 contains cylinders 601A and 601B. Cylinders 601A and 601B areeach partitioned by a piston, 640A and 640B, respectively, into apneumatic cavity, 637A and 637B, and an hydraulic cavity, 638A and 638B.Pneumatic cavity 637A is connected to pneumatic distributor 636 viapneumatic conduit 658A, and 637B is connected via 658B. Hydrauliccavities 638A and 638B are connected via hydraulic conduits 659A, twomagnetorheological valves 648A and hydraulic accumulator 649A. Drive 647operates in the same manner as described for drive 646.

FIG. 8 shows a trainer, suitable for use in developing or diagnosingmuscle strength, using magnetorheological elements. The trainer consistsof two preferably identical hydraulic cylinders 801 fastened to anholder 862 by means of an adjustment unit 863. Adjustment unit 863allows the position and orientation of the hydraulic cylinders to beadjusted to provide desirable conditions for the user. The hydrauliccylinders 801 are rigidly connected, via holder 862, to a trainer base869, and an adjustable user's seat 867 is mounted to the base 869.

In each cylinder 801, a piston 840 is rigidly connected via a rod 841with an element 864 carrying pedal load. The cavities of the hydrauliccylinders 801 are filled with a polarizing structure-reversible medium,such as magnetorheological fluid polarized by a magnetic field. Thecavities are connected by an hydraulic drive 865 composed of threesections: first and second sections 865', each of which is in the rangeof a controlled polarizer 802, and a measuring section 865", to which apressure meter 866 is connected. Each section 865 is filled withmagnetorheological fluid, as illustrated. For ease of manufacture andrepair, sections 865' and section 865" of the hydraulic drive maycomprise a single two-channel valve 868 such as the valve illustrated inFIG. 3. If a valve such as is illustrated in FIG. 3 were used, thepressure meter 866 would be connected to the connecting pipe 316. Thevalve 868 is connected to an electric supply source 811.

The polarizers 802 are connected through lines 812 to an electric supplysource 811. By varying the current supplied to polarizers 802, theintensity of the magnetic field in the magnetorheological drive 865 canbe varied. The corresponding increase or decrease in the viscosity ofthe magnetorheological fluid will cause an increase or decrease in theresistance of pedal 864 to movement. In one embodiment of the trainer,the force required to move the pedal may be varied from 1-100 kg, thepower of the controlling current to the magnetorheological valve is nomore than 10 W, and the volume of magnetorheological fluid employed inthe system is 1-1.5 liters.

The electric supply source 811 may be connected with a program controldevice 855, such as a microprocessor, programmable controller, orpersonal computer. The load may therefore be controlled manually or in aprogrammed regime.

FIG. 9 illustrates a driver's seat using a magnetorheological dashpot toprovide suspension in, for example, a tractor, road machine, or similarvehicle. The suspension comprises a base 969 on which one or morepillars 971 are fixed. Axles 972 are located on the pillars 971, and alever system 970 is mounted to the axles 972. Movable magnetorheologicalload-bearing elements 973 are located between the lever system 970 andthe base 969. Load-bearing elements 973 may be bellows, hydrauliccylinders, or other similar means, wherein one end of the load-bearingelement may be held stationary and another end may be elasticallyextended and retracted. The stationary end of each load-bearing element973 is connected with base 969. The hydraulic cavity of eachload-bearing element 973 is filled with a magnetorheological fluid 943,and the load-bearing elements 973 are connected with each other via amagnetorheological valve 948. Magnetorheological valve 948 iselectrically connected to a control system 955. A vibration isolationmass 967, such as a driver and seat, is located on one end of the leversystem 970, and the opposite end of the lever system 970 is connectedwith base 969 via an elastic coupling 974.

The suspension system operates as follows. When the vehicle moves, thevehicle base 969 vibrates, and the mass 967 shifts relative to base 969,thus rotating lever system 970 on axles 972. The movement of leversystem 970 causes elastic coupling 974 to deform, and displaces themoving parts of load-bearing elements 973. In this case, while one ofthe elements 973 is extended, another is compressed. Thus, vibrations ofmass 967 relative to base 969 cause magnetorheological fluid to bepumped through magnetorheological valve 948 from one load-bearingelement 973 to another. Varying the hydraulic resistance of themagnetorheological valve by control system 955 results in changes of thedissipative parameters of vibrations, which may be used for reducing theamplitude of vibrations, their damping time, and vibration overloads.The advantages of this system are its simple, highly efficient designthat provides flexibility and quick reaction rates at a low cost.

FIG. 13 illustrates the effects of the magnetorheological vibrationsystem described above and shown in FIG. 9. FIG. 13 depicts the cushionseat to suspension base acceleration amplitude ratio as a function ofexciting oscillations. As illustrated, increasing the throttle valvecurrent I sharply reduces resonance accelerations and varies theresonance frequency. Both of these factors may successfully be used foreffective control of a seat suspension. Based on this principle, it ispossible to design automatic suspensions of numerous devices, includingbearing wheels of transport vehicles, vibration-isolation systems ofdevices, tools, and materials to be transported.

A schematic of another pneumatic magnetorheological drive is shown inFIG. 10. In the drive shown there are two cylinders, a pneumaticcylinder 1037 and an hydraulic cylinder 1038. A piston 1034A connectedto a rod 1041A partitions the pneumatic cylinder into two chambers 1037Aand 1037B, and a piston 1034B connected to a rod 1041B partitions thehydraulic cylinder into two chambers 1038A and 1038B. Rods 1041A and1041B are rigidly connected to each other, and are engaged with anactuator 1039.

Chambers 1037A and 1037B of pneumatic cylinder 1037 are connected with apneumatic distributor 1036 which connects them with either a pneumaticsystem 1035 or environment.

Chambers 1038A and 1038B of the hydraulic cylinder are filled withmagnetorheological fluid, and are connected to each other via amagnetorheological valve 1048, such as those described above.Magnetorheological valve 1048 is connected to a control system 1055.

To move the actuator 1039, pneumatic distributor 1036 supplies air frompneumatic system 1035 to pneumatic chamber 1037A, and the air pressurein pneumatic chamber 1037A is increased. As the air pressure isincreased, piston 1034A moves in the direction of actuator 1039. Rigidlyconnected rods 1041A and 1041B, piston 1034B, and actuator 1039 movewith piston 1034A in the direction of the actuator 1039. As rods 1041Aand 1041B and pistons 1034A and 1034B move, magnetorheological fluidflows through magnetorheological valve 1048. To slow or stop the motion,control system 1055 varies the strength of the magnetic field inmagnetorheological valve 1048. Thus, the speed of the drive may becontrolled and the actuator may be accurately positioned.

Chamber 1038A and magnetorheological valve 1048 are connected with anhydraulic accumulator 1049, which compensates for changes in the volumeof magnetorheological fluid in the hydraulic cylinder when the piston1034B moves. The hydraulic accumulator 1049 also accumulates excesshydraulic system pressure, which is necessary to improve the rigidity ofthe drive and its dynamic characteristics, and the accumulator 1049facilitates replenishment of magnetorheological fluid when necessary.

Thus the pneumatic magnetorheological drive shown in FIG. 10 allows forcontrol over a wide range of speeds, and may be positioned preciselywithout stops. Moreover, the ability to control the drive at all stagesof deceleration enables one to avoid undesirable accidents even at highspeeds. Some advantages of the pneumatic magnetorheological drive arethat it uses a convenient energy carrier (compressed gas) and a simplescheme of providing accurate positioning and quick-response. The driveis also highly reliable and fire-safe. And it offers the flexibility ofchanging the programming. Such devices are promising in the design ofmultipurpose positioning drives for different fields of mechanicalengineering.

FIG. 11 shows a control scheme, using magnetorheological fluid, forhydraulic cylinder piston motion under active operating conditions.Hydraulic cylinder 1138 is partitioned into two chambers 1138A and 1138Bby piston 1134, which is connected to rod 1141. Magnetorheologicalvalves 1148A, 1148B, 1148C, and 1148D are connected with each other andwith hydraulic chambers 1138A and 1138B via hydraulic conduit 1159.Hydraulic cylinder 1138 and hydraulic conduit 1159 are filled withmagnetorheological fluid 1143. Pump 1180 causes the magnetorheologicalfluid 1143 to flow in only one predetermined direction in hydraulicconduit 1159.

Conducting a current through the windings of the diagonally locatedmagnetorheological valves 1148A and 1148D, or through valves 1148B and1148C, varies the hydraulic resistance, thereby yielding a pressure dropin the cylinder chamber corresponding to valve resistance, and causingcorresponding displacement of the piston 1134. For example, conductingsufficient current through the windings of magnetorheological valves1148A and 1148D to close them will cause the magnetorheological fluid toflow from chamber 1138B, through magnetorheological valve 1148C, pump1180, and magnetorheological valve 1148B, into chamber 1138A. Thusclosing valves 1148A and 1148D will move piston 1134 toward the bottomof hydraulic cylinder 1138.

This magnetorheological system may carry out movements according to themagnetorheological valve winding current supplied. An important featureof such a drive is its ability to reliably fix the actuator at a desiredpositioning point.

FIG. 12 shows a schematic of a system for stabilizing an object with anactive magnetorheological drive. In the stabilization system shown, anobject is stabilized by the interaction of a magnetorheological driveand a light sensing means. An object 1288 is placed in movable frame1290. Movable frame 1290 is supported by magnetorheological load-bearingelements 1273A and 1273B, which are connected to hydraulic conduit 1259,and frame support 1291. Magnetorheological valves 1248A, 1248B, 1248C,and 1248D and a pump 1280 regulate the flow of magnetorheological fluid1243 to magnetorheological load-bearing elements 1273A and 1273B.Magnetorheological valves 1248A, 1248B, 1248C, and 1248D are connectedto a control system 1255.

A mirror system 1286, comprised of movable mirror 1286A, mirror 1286Bmounted on the object to be stabilized 1288, and mirror 1286C, reflectslight generated by a laser source 1285. A vibration-causing device 1287creates a disturbance in the light beam with a frequency and amplitudeto be regulated, which is carried through the mirror system 1286 andprojected onto a sensing means 1289. The sensing means 1289 measures thedisturbance and generates an error signal of proportional amplitude to acontrol system 1255. In a preferred embodiment, the sensing means is aphotodiode.

In operation, the laser source 1285 generates a beam of light which isreflected by mirror 1286A. The vibration causing device 1287 causes adisturbance in the light beam reflected by mirror 1286A. The light beamtravels from mirror 1286A, to mirror 1286B, to mirror 1286C, to sensingmeans 1289. Sensing means 1289 measures the disturbance in the lightbeam and generates an error signal proportional to the amplitude of thedisturbance. The error signal generated by the sensing means 1289 isreceived by the control device 1255, and output signals are sent to themagnetorheological valves 1248A, 1248B, 1248C, and 1248D. Varying thepressure in a pair of magnetorheological valves, such as 1248A and1248D, redistributes the pressure in the load-bearing elements 1273A and1273B and causes movable frame 1290 to pivot on frame support 1291,thereby displacing the object 1288 by an angle proportional to the valueof the error signal generated by the sensing means 1289.

In tests of the above system, the object positioning error did notexceed 0.5 of an angular second over a frequency range up to 250 Hz.

Two or more one-coordinate load-bearing elements 1273 may be combined toform a multi-coordinate stabilization system. Such a multi-coordinatesystem may be used to dampen multi-dimensional vibrations in morecomplex systems. One possible use of such devices is in mirrorpositioning systems for lasers.

We claim:
 1. A pneumohydraulic positioning device comprising:at leastone magnetoconducting cylinder partitioned into at least two chambers bya partition, wherein one chamber contains a magnetorheological fluid,and a second chamber contains a gas; a pulley unit, wherein one end ofthe unit is attached to the partition, and a second end of the unit isattached to a carriage; an actuator attached to the carriage; at leastone magnetorheological valve coupled with the chamber of themagnetoconducting cylinder containing magnetorheological fluid forvarying the viscosity of magnetorheological fluid flowing through saidvalve; a source of compressed gas coupled with the chamber of themagnetoconducting cylinder containing a gas; and a program controldevice coupled with the pulley unit, the source of compressed gas, andthe magnetorheological valve.
 2. An exercise machine comprising:at leastone magnetoconducting cylinder partitioned into at least two chambers bya piston head, wherein one chamber contains a magnetorheological fluid,and a second chamber contains a gas; a load-carrying rod extendingthrough the magnetoconducting cylinder from the piston head to a pointexternal to the magnetoconducting cylinder; and at least onemagnetotheological valve connected to the chamber of themagnetoconducting cylinder containing magnetorheological fluid forvarying the viscosity of magnetorheological fluid flowing through saidvalve.
 3. A vibration damping system comprising:a lever system,supporting a vibrating load, connected to a base by a support pillar; anelastic coupling connected to the lever system and the base; at leastone magnetorheological load-bearing element positioned between the leversystem and the base, said element including a hydraulic cavitycontaining magnetorheological fluid; and a magnetorheological valveconnected with the hydraulic cavity of the magnetorheologicalload-bearing element for varying the viscosity of the magnetorheologicalfluid flowing through said valve.
 4. A pneumohydraulic drive,comprising:two main cylinders, each partitioned into two chambers by apartition wherein one chamber contains a magnetorheological fluid andthe other chamber contains a gas; a hydraulic system connected to thechambers of said cylinders containing magnetorheological fluid, saidhydraulic system including an hydraulic accumulator and at least onemagnetorheological valve for varying the viscosity of magnetorheologicalfluid flowing through said valve; a flexible member having one endconnected to one of said partitions and an opposite end connected to theother of said partitions; and a carriage connected to said flexiblemember.